Experimental And Numerical Investigation On Heat Transfer And Fluid Flow Characteristics Of Fin-and-tube Heat Exchangers

The plate-fin-and-tube heat exchanger, as a high-performance compact heat exchanger, is widely used in power, chemical, petrochemical, refrigeration engineering. Currently, it is one of the most used heat exchanger. To study and analyse the characteristics of fin-tube heat exchanger not only has important practical significance, but also is an important role in promoting the current energy conservation and pollutants discharge reduction. Fin structure has a great impact on the heat exchanger performance, which encouraged many scholars to do research on the fin structures for heat transfer enhancement. Many research achievements have been made on the plain fins and people summarized some empirical formulas with high accuracy which could be used for reference when designing heat exchangers, but for some other fin patterns, especially for the new designed ones, it is hard to find empirical formulas with enough accuracy to predict the performance of heat exchangers, experimental study is still the best method.In this study, plain fin and new slitted fin with two fin spacing (2.1mm,2.3mm) are tested under different air velocities (1～5m/s) and water-side temperatures (45℃,(79,80,82,90)℃). Results indicates that, for the tested fin spacing, plain fin gets higher h as the fin spacing grows, while slitted fin has reverse result, but both them has lower△P. Under different air velocities, the h of plain fin is between44～93.7W/m2·℃and the h of slitted fin is63～138for the2.1mm fin spacing, for the2.3mm fin spacing, the h of plain fin is between58-104W/m2·℃and the h of slitted fin is52.7～131.7.Compare these two fin structures, the h of slitted fin is26%-47.7%higher but△P is also increased by34.4%～42.9%. The heat transfer and friction correlations given in this study are valuable for designing plate-fin-and-tube heat exchangers.The numerical simulation result shows that the heat transfer power gets lower along the tube row direction, the first row has the highest heat transfer power, about48.3%～81%of total and the highest pressure drop, about21.5%～23.3%of total. Compared the experimental result with the numerical result, there is a certain deviation, for pressure drop comparison this deviation is even larger, but both two have the same trend. That means numerical simulation has a certain degree of reliability, but the result accuracy should be enhanced. Discussions believe that the mesh generation quality has a great impact on the numerical result, Improving the quality of mesh generation to obtain more accurate result could make the numerical simulation method more reliable in heat exchanger performance study use. The numerical method is limited in being used on simulating heat transfer performance of fin-and-tube heat exchangers.